Binder composition, coating compositions containing this binder composition, production and use thereof

ABSTRACT

Binder composition, coating compositions produced therefrom and use thereof, in particular for multi-layer lacquer coatings. The binder composition contains: 
     A) 25 to 75 wt. % of the reaction product of one or more carboxy-functionalised (meth) acrylic copolymers containing urethane groups and/or of one or more carboxy-functionalised polyesters containing urethane groups, each having an acid value of 30 to 200 mg of KOH/g, with one or more lactones, 
     B) 25 to 75 wt. % of one or more epoxy-functionalised crosslinking agents having at least two epoxy functions per molecule with a number average molecular weight (Mn) of 200 to 10000 g/mol, 
     C) 0 to 60 wt. % of one or more polyols having at least two hydroxyl functions per molecule, 
     D 1 ) 0 to 20 wt. % of one or more melamine resins, 
     D 2 ) 0 to 40 wt. % of one or more free or capped polyisocyanates, wherein the sum of the weight percentages of components A), B), C), D 1 ) and D 2 ) amounts to 100 wt. %, together with 
     E) 0 to 10 wt. % of one or more catalysts to catalyse the reaction of carboxyl and epoxy groups, relative to the sum of weights of components A) to D 2 ).

This invention relates to binder compositions suitable for theproduction of coating compositions, which are stoved at elevatedtemperature and are in particular suitable for the production ofmulti-layer lacquer coatings, for example in the automotive sector.

DE-A-30 22 996 discloses a storing lacquer in which polymers containingcarboxyl groups, such as for example acrylates based on acrylic acid ormethacrylic acid and acrylates containing glycidyl groups are combinedto yield a curable composition.

WO 84/00771 describes a multi-component system in which four types ofbinder are mixed together and then applied. The components comprise anacrylate containing hydroxyl groups, acid anhydride, wherein at least50% are alkylhexahydroxphthalic anhydrides, epoxy resin and melamineresin. The systems have an elevated solids content.

DE-A-23 33 384 describes a binder based on acrylated polyesters, whichare obtained by polymerising an acrylate containing hydroxyl groups in apolyester or alkyd resin containing hydroxyl groups. Crosslinking may beperformed with melamine resins and epoxy resins simultaneously.

DE-A-38 00 389 describes the modification of copolymers containinghydroxyl groups with lactones, in particular with epsilon-caprolactone.

U.S. Pat. No. 4,501,829 describes polyesters having hydroxyl andcarboxyl groups, which are reacted with lactones. The reaction proceedson the hydroxyl groups. U.S. Pat. No. 4,082,816 describes compositionsof (meth)acrylic copolymers containing carboxyl groups and modified withcaprolactone and melamine/formaldehyde resins.

The as yet unpublished German patent application P 42 37 658 describesbinder compositions which are composed of lactone-modified polyacrylatesor polyesters containing carboxyl groups and polymers containingglycidyl groups. Urethanisation of the acidic components is notmentioned.

Some of the stated coating compositions give rise to films havingelevated hardness and good weathering resistance. They do not, however,fulfil the constantly rising requirements for elevated resistance toacids and solvents.

The object of the invention is to provide a binder system which may beprocessed to yield coating compositions which may be stored at elevatedtemperature to yield coatings having good hardness, good weatheringresistance and elevated elasticity and which are additionally resistantto acids and solvents. The coating compositions should additionallyexhibit good application characteristics (reduced tendency to sag) evenat elevated layer thicknesses.

It has been found that this object may be achieved by a bindercomposition which is provided by this invention and contains:

A) 25 to 75 wt. % of the reaction product of one or morecarboxy-functionalised (meth)acrylic copolymers containing urethanegroups and/or of one or more carboxy-functionalised polyesterscontaining urethane groups, each having an acid value of 30 to 200 mg ofKOH/g, with one or more lactones,

B) 25 to 75 wt. % of one or more epoxy-functionalised crosslinkingagents having at least two epoxy functions per molecule with a numberaverage molecular weight (Mn) of 200 to 10000 g/mol,

C) 0 to 60 wt. % of one or more polyols having at least two hydroxylfunctions per molecule,

D₁) 0 to 20 wt. % of one or more melamine resins,

D₂) 0 to 40 wt. % of one or more free or capped polyisocyanates, whereinthe sum of the weight percentages of components A), B), C), D₁) and D₂)amounts to 100 wt. %, together with

E) 0 to 10 wt. % of one or more catalysts to catalyse the reaction ofcarboxyl and epoxy groups, relative to the sum of weights of componentsA) to D₂).

It has been found that the binder compositions according to theinvention or the coating compositions produced therefrom give rise tocoatings which have elevated solvent resistance, in particular towardsxylene, even in the case of the purest possible crosslinking betweencarboxyl groups and epoxy groups, such that it is possible to workwithout or only with small quantities of additional crosslinking agentssuch as polyisocyanates and/or melamine resins.

According to a preferred embodiment of the invention, thecarboxy-functionalised (meth)acrylic copolymers containing urethanegroups, which may be reacted with lactone according to component A),have a number average molecular weight (Mn) of 1000 to 30000 g/mol. Thecarboxy-functionalised polyesters containing urethane groups which maycorrespondingly be used preferably have a calculated molecular weight of500 to 4000 g/mol, for example of 800 to 4000 g/mol. The acid value ofthese starting materials is 30 to 200 mg of KOH/g, preferably from 30 to140 mg of KOH/g and particularly preferably from 60 to 120 mg of KOH/g.

This invention also relates to coating compositions which may beproduced from the binder compositions according to the invention. Thesemay be aqueous and/or solvent-based coating compositions, which mayoptionally contain pigments, extenders and/or conventional lacquerauxiliary substances and additives; they may also be formulated assolvent-free and anhydrous powder coatings.

The carboxyl groups in component A) of the binder or coatingcompositions according to the invention are modified by reaction withlactones. Attaching the lactones "chain extends" the carboxyl groups.The carboxyl groups originally located on the (meth)acrylic copolymerskeleton and/or on the polyester skeleton are esterified by ring-openingof the lactone to be attached, wherein the lactone/carboxyl groups are,however, released, so yielding reaction products having exposed carboxylgroups on the short side chains corresponding to the lactone.

During the production of the (meth)acrylic copolymers or polyesterscontaining urethane and carboxyl groups and used to prepare componentA), the carboxyl groups may be introduced directly by using structuralunits containing carboxyl groups, for example during synthesis ofpolymers, such as (meth)acrylic copolymers. Examples of suitablemonomers containing carboxyl groups which may be used for this purposeare unsaturated carboxylic acids, such as for example acrylic,methacrylic, itaconic, crotonic, isocrotonic, aconitic, maleic andfumaric acid, semi-esters of maleic and fumaric acid together withbeta-carboxyethyl acrylate and adducts of hydroxyalkyl esters of acrylicacid and/or methacrylic acid with carboxylic anhydrides, such as forexample phthalic acid mono-2-methacryloyloxyethyl ester.

The term (meth)acrylic is used in the present description and the patentclaims. This means acrylic and/or methacrylic.

It is, however, possible during production of the (meth)acryliccopolymers or polyesters containing urethane and carboxyl groupsinitially to synthesise a polymer containing hydroxyl and optionallycarboxyl groups having an OH value of 30 to 200 mg of KOH/g andpartially or entirely to introduce the carboxyl groups in a second stageby reacting the polymers containing hydroxyl and optionally carboxylgroups with carboxylic anhydrides. The quantity ratios used in thismethod must, however, be such that sufficient OH groups remain in orderto be able to urethanise the (meth)acrylates.

Carboxylic anhydrides suitable for addition onto the polymers containinghydroxyl groups are the anhydrides of aliphatic, cycloaliphatic andaromatic saturated and/or unsaturated di- and polycarboxylic acids, suchas for example the anhydrides of phthalic acid, tetrahydrophthalic acid,hexahydrophthalic acid, succinic acid, maleic acid, itaconic acid,glutaric acid, trimellitic acid and pyromellitic acid, together with thehalogenated or alkylated derivatives thereof.

The anhydrides of phthalic acid, tetrahydro- and hexahydrophthalic acidtogether with 5-methylhexahydrophthalic anhydride are preferably used.

Examples of hydroxyalkyl esters of alpha,beta-unsaturated carboxylicacids containing primary hydroxyl groups suitable for the production ofhydroxy-functional poly(meth)acrylates are hydroxyethyl acrylate,hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyamyl acrylate,hydroxyhexyl acrylate, hydroxyoctyl acrylate and the correspondingmethacrylates. Examples of usable hydroxyalkyl esters containing asecondary hydroxyl group which may be mentioned are 2-hydroxypropylacrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate and thecorresponding methacrylates.

The hydroxy-functionalised component may advantageously at leastpartially be a reaction product prepared from one mol of hydroxyethylacrylate and/or hydroxyethyl methacrylate and an average of 2 mol ofepsilon-caprolactone.

A reaction product prepared from acrylic acid and/or methacrylic acidwith the glycidyl ester of a carboxylic acid containing a tertiaryalpha-carbon atom may also be used as at least a proportion of thehydroxy-functionalised component. Glycidyl esters of highly branchedmonocarboxylic acid are available, for example, under the trade name"Cardura". The reaction of the acrylic acid or methacrylic acid with theglycidyl ester of a carboxylic acid containing a tertiary alpha carbonmay be performed before, during or after the polymerisation reaction.

In addition to the above-stated monomers, it is also possible to usefurther ethylenically unsaturated monomers in the production of the(meth)acrylic copolymers. Selection of the further ethylenicallyunsaturated monomers is not critical. Care must merely be taken toensure that incorporation of these monomers does not give rise toundesirable copolymer properties.

Alkyl esters of acrylic and methacrylic acid are in particular suitableas a further ethylenically unsaturated component, such as for examplemethyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate,pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, 3,5,5-trimethylhexyl(meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, hexadecyl(meth)acrylate, octadecyl (meth)acrylate and octadecenyl (meth)acrylate.It is also possible to use silane-modified monomers, such as for examplegamma-methacryloxypropyl-trimethoxysilane orgamma-methacryloxypropyl-tris(2methoxyethoxy)silane.

Further ethylenically unsaturated monomers may be used instead of theabove-stated acrylic and methacrylic acid alkyl esters or as well asthese alkyl esters for the production of (meth)acrylic copolymers,wherein selection of these monomers is largely directed by the desiredproperties of the coating composition with regard to hardness,elasticity, compatibility and polarity.

Examples of further suitable ethylenically unsaturated monomers are thealkyl esters of maleic, fumaric, tetrahydrophthalic, crotonic,isocrotonic, vinylacetic and itaconic acid, such as for example thecorresponding methyl, ethyl, propyl, butyl, isopropyl, isobutyl, pentyl,amyl, isoamyl, hexyl, cyclohexyl, 2-ethylhexyl, octyl,3,5,5-trimethylhexyl, decyl, dodecyl, hexadecyl, octadecyl andoctadecenyl esters.

Small proportions of monomers containing at least two polymerisable,olefinically unsaturated double bonds may also be used. The proportionof these monomers is preferably below 5 wt. %, relative to the totalweight of the monomers.

Examples of such compounds are hexanediol diacrylate, hexanedioldimethacrylate, ethylene glycol diacrylate, ethylene glycoldimethacrylate, butanediol diacrylate, butanediol dimethacrylate,hexamethylenebismethacrylamide, trimethylolpropane triacrylate,trimethylolpropane trimethacrylate and similar compounds.

Monovinyl aromatic compounds are another suitable component. Theypreferably contain 8 to 9 carbon atoms per molecule. Examples ofsuitable compounds are styrene, vinyltoluene, alpha-methylstyrene,chlorostyrene, o-, m- or p-methylstyrene, 2,5-dimethylstyrene,p-methoxystyrene, p-tert.-butylstyrene, p-dimethylaminostyrene,p-acetamidostyrene and m-vinylphenol. Vinyltoluenes and in particularstyrene are preferably used.

The monomers or the monomer mixture used may contain initiators. In theevent that initiators are not present in the monomer mixture, they maybe added to the monomer mixture optionally with a slight delay orseparately apportioned. Polymerisation may then be continued for arelatively extended period, for example several hours. It is thenpossible to use a conventional lacquer solvent to establish a desiredsolids content, for example of the order of 30 to 60 wt. %, for exampleof 50 wt. %.

The binders are produced by free-radical copolymerisation. The quantityof monomer is adjusted in such a manner that the desired specificationswith regard to molecular weight, OH group ratio, OH value and acid valueare achieved. It may prove advantageous to add a proportion of themonomers with delay relative to the remainder.

Production proceeds, for example, by free-radical solutionpolymerisation in the presence of a free-radical initiator, as isfamiliar to the person skilled in the art. Examples of free-radicalinitiators are dialkyl peroxides, such as di-tert.-butyl peroxide,dicumyl peroxide; diacyl peroxides, such as dibenzoyl peroxide,dilauroyl peroxide; hydroperoxides, such as cumene hydroperoxide,tert.-butyl hydroperoxide; peresters, such as tert.-butyl perbenzoate,tert.-butyl perpivalate, tert.-butyl per-3,5,5-trimethylhexanoate,tert.-butyl per-2-ethylhexanoate; peroxydicarbonates, such asdi-2-ethylhexyl peroxydicarbonate, dicyclohexyl peroxydicarbonate;perketals, such as1,1-bis-(tert.-butylperoxy)-3,5,5-trimethylcyclohexane,1,1-bis-(tert.-butylperoxy)cyclohexane; ketone peroxides, such ascyclohexanone peroxide, methyl isobutyl ketone peroxide and azocompounds, such as 2,2'-azo-bis-cyclohexanecarbonitrile,azo-bis-isobutyronitrile, C--C cleaving initiators, such as for examplebenzopinacole derivatives.

The polymerisation initiators are generally used, for example, in aquantity of 0.1 to 4 wt. %, relative to the weight of monomers.

In order to urethanise the carboxy-functionalised (meth)acryliccopolymers, OH functions of the carboxy-functionalised (meth)acryliccopolymers must be reacted with mono-, di-, tri- or polyisocyanates in afurther reaction stage. The quantity of the di-, tri- or polyisocyanatesis dependent upon the OH value of the (meth)acrylic copolymer and mustbe selected such that gelation is avoided. For example, copolymershaving an OH value of 30 to 100 mg of KOH/g are reacted with di-, tri-or polyisocyanate in such a manner that the resultant urethanisedcopolymer has an OH value of 15 to 80 mg of KOH/g. This procedure may beperformed in such a manner that the carboxy- and OH-functional(meth)acrylic copolymer is initially introduced into a vessel dissolvedin an aprotic solvent and the di-, tri- or polyisocyanate, optionallydissolved in an aprotic solvent such as for example xylene or butylacetate, is then apportioned within a period of, for example 30 minutesto 3 hours at 5° C. to 80° C. The reaction is complete once the NCOvalue of the reaction mixture is less than 0.1. When monoisocyanates areused, it is not necessary to restrict the quantity of isocyanate as allthe OH functions of the (meth)acrylic copolymer may optionally bereacted. The reaction conditions are the same as for di-, tri- orpolyisocyanates. It is, of course, also possible to urethanise theOH-functional (meth)acrylic copolymers before the introduction ofcarboxyl groups by reaction with acid anhydrides and only thereafter toattach the acid. Examples of di-, tri- and polyisocyanates, which mayalso be used as a mixture, are described in the description of componentD₂).

Examples of monoisocyanates are, for example, reaction products of thediisocyanates described for component D₂) with monoalcohols, such asmethanol, butanol, hexanol or octanol, wherein 1 mol of diisocyanate isreacted with 1 mol of alcohol. Further examples of monoisocyanates arealpha,alpha-dimethyl-m-isopropenylbenzyl isocyanate orisocyanatoacrylate.

The polymers containing urethane and carboxyl groups used for theproduction of component A) are copolymers containing carboxyl groupsand/or polyesters containing carboxyl groups. The polyesters containingcarboxyl groups may be synthesised using conventional methods (c.f. forexample B. Vollmert, Grundriβ der makromolecularen Chemie, E. VollmertVerlag, Karlsruhe 1982, volume II, pp. 5 et seq.) from aliphatic and/orcycloaliphatic di-, tri- or more highly hydric alcohols, optionallytogether with monohydric alcohols and from aliphatic, aromatic and/orcycloaliphatic carboxylic acids together with polycarboxylic acids ofgreater basicity. Examples of suitable alcohols are ethylene glycol,1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol,1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5pentanediol,3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-ethyl-1,6-hexanediol,2,2,4-trimethyl-1,6-hexanediol, 1,4-dimethylolcyclohexane, glycerol,trimethylolethane, trimethylolpropane, pentaerythritol, etherificationproducts of diols and polyols, for example di- and triethylene glycol,polyethylene glycol, neopentyl glycol esters of hydroxypivalic acid.

Examples of suitable carboxylic acids are adipic, azelaic, 1,3- and1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic, hexahydrophthalic,endomethyltetrahydrophthalic acid, isophthalic acid, o-phthalic acid,terephthalic acid or the anhydrides thereof and the esterifiablederivatives thereof.

The calculated molecular weights of the polyesters are, for example,from 500 to 4000 g/mol, preferably between 500 and 2000 g/mol.

The carboxy-functional (meth)acrylic copolymers and polyesters usablefor the production of component A) are "chain extended" with a lactone.The lactones (cyclic ethers) attach themselves to carboxyl groups,wherein the ring is opened and a new terminal carboxyl group arises.Since, in the presence of OH and COOH groups, the OH groups reactsubstantially faster with lactones, preferred carboxy-functional(meth)acrylic copolymers and carboxy-functional polyesters for theproduction of component A) are those which contain no OH groups. Ifcopolymers or polyesters containing OH groups are used as startingmaterials, the OH groups thereof are preferably entirely or largelyreacted with anhydrides to yield carboxylic acids. An example of aparticularly preferred lactone is epsilon-caprolactone.

Examples of other lactones are gamma-butyrolactone and lactones, such asbeta-propiolactone, delta-valerolactone, delta-butyrolactone,zeta-enantholactone, eta-caprolactone. Such lactones may be substituted;examples of substituted lactones are 6-methyl-epsilon-caprolactone,3-methyl-epsilon-caprolactone, 5-methyl-epsilon-caprolactone,5-phenol-epsilon-caprolactone, 4-methyl-delta-valerolactone,3,5-dimethyl-epsilon-caprolactone and mixtures thereof.

The reaction with the lactone may, for example, proceed immediatelyafter resin synthesis, i.e. after synthesis of the poly(meth)acryliccopolymer and/or of the polyester. The reaction proceeds, for example,at elevated temperature, for example at temperatures of up to 100° C.The reaction may, for example, be performed with stirring for, forexample, up to 10 hours.

Like the carboxy-functionalised (meth)acrylic copolymers alreadydescribed, the acidic polyesters are urethanised. The reactionconditions are the same as for the (meth)acrylic copolymers. It ispossible to introduce urethane groups by 1) reacting the carboxy- andOH-functional polyester, by 2) reacting the lactone-modifiedcarboxy-functional and OH-functional polyesters with mono-, di- or tri-or polyisocyanates. It is preferred to react carboxy- and OH-functionalpolyesters with polyisocyanates before lactonisation. In this manner, itis possible to urethanise a large proportion or the entirety of the OHgroups, so that, in the event of reaction with lactone, these OH groupscan no longer enter into competitive reactions with carboxyl groups.

It is also possible to introduce the urethane groups during thesynthesis of the polyesters themselves. This is achieved by entirely orpartially replacing di- or tricarboxylic acids with di- ortriisocyanates.

Methods 1) and 2) above are preferred, with method 1) being particularlypreferred. Examples of usable mono-, di-, tri- or polyisocyanates arestated in the description of component D₂).

The binder composition according to the invention, or the coatingcompositions according to the invention contain as component B) one ormore epoxy-functionalised compounds containing at least two epoxyfunctions per molecule and having a number average molecular weight (Mn)of 200 to 10000 g/mol.

Examples of such compounds are conventional di- or polyepoxides, forexample polyglycidyl ethers based on diethylene glycol, dipropyleneglycol, polypropylene glycol having a number average molecular weight(Mn) of up to 2000, triglycidyl ethers of glycerol and/or di- orpolyphenols such as bisphenol A.

Further examples of di- or polyepoxides are those based on di- orpolyglycidyl esters. Examples of these are reaction products preparedfrom 1-hydroxy-2,3-epoxypropane with phthalic or terephthalic acid toyield phthalic or terephthalic acid bis(2,3-epoxypropyl ester) or of adiglycidyl ether of bisphenol A with trimellitic anhydride to yieldpolyesters having a number average molecular weight (Mn) of 500 to 2000.

Further examples which may also be used are glycidyl-functionalised(meth)acrylic copolymers. Examples of these are copolymers of glycidyl(meth)acrylate or 2,3-epoxy-cyclopentyl acrylate. Comonomers which maybe selected are esters of (meth)acrylic acid, such as for examplemethyl, ethyl, butyl, isobutyl, ethylhexyl, cyclohexyl and/or lauryl(meth)acrylate, hydroxy-functionalised esters of (meth)acrylic acid,such as for example hydroxyethyl and/or hydroxypropyl ester, togetherwith styrene, vinyltoluene and/or alpha-methylstyrene as well as allalpha,beta-unsaturated monomers as have already been described above forcomponent A). The number average molecular weight (Mn) may, for example,be between 1000 and 10000, preferably from 2000 to 5000. Furthercopolymerisable glycidyl monomers are, for example, (meth)allylglycidylethers or 3,4-epoxy-1-vinylcyclohexane. The copolymers are produced byfree-radical solution polymerisation, which is known to the personskilled in the art and requires no further explanation.

It is also possible at least partially to precondense binder componentsA and B in a further reaction stage. This may, for example, be achievedby heating components A and B together. The desired degree ofcondensation may, for example, be determined by the reduction in acidvalue. It is, for example, possible to heat the mixture to temperaturesof for example 80° to 120° C. with stirring and to continue stirringuntil the acid value of the mixture has fallen by, for example, 2 to 5mg of KOH/g of solid resin. It is, of course, also possible to reducethe acid value further, in which case care should be taken to ensurethat the viscosity of the mixture does not increase as far as gelation.The storage stability of the compositions may be further increased byprecondensation of components A) and B). Precondensation betweencomponents A) and C) is also possible and the conditions are the same asthose for condensation of A) and B). It is also possible to synthesisebinder B) as a graft on binder C) or vice versa.

To this end, it is, for example, possible initially to introduce part orall of the component C) polyol into a vessel, optionally with one ormore organic solvents, and to react therein the monomers necessary forthe production of the epoxy-functional component B) or a proportionthereof. For example, the polyols C), optionally with solvent, may beinitially introduced into a vessel and heated, for example totemperatures of the order of 140° C. The monomers necessary for theproduction of the epoxy-functional component B), optionally togetherwith initiators, may be apportioned, for example over a period of up to5 hours. The polyol component C), as defined in greater detail below,used in this method is preferably a polyester polyol, in particular sucha compound having a number average molecular weight Mn of 500 to 2000,preferably having an acid value of below 3 mg of KOH/g and preferablyhaving an OH value of 15 to 200 mg of KOH/g. Such a precondensationproduct (graft copolymer) prepared from B) and C) may have advantagesover a mixture of B) and C), such as for example better compatibilityand more homogeneous mixing.

The binder composition according to the invention or the coatingcompositions according to the invention may contain one or more polyolscontaining at least two hydroxyl functions per molecule as component C).These polyols may, for example, be selected from among

a) polyols from the group comprising linear or branched alkane di- andpolyols having 2 to 12 carbon atoms, or

b) poly(meth)acrylates or poly(meth)acrylamides containing hydroxylgroups and based on (meth)acrylic acid hydroxyalkyl esters having 2 to12 carbon atoms in the alkyl portion or (meth)acrylic acidhydroxy-alkylamides having 2 to 12 carbon atoms in the alkyl portion,optionally copolymerised with alpha,beta-unsaturated monomers having anumber average molecular weight Mn of 1000 to 10000, or

c) poly(meth)acrylates containing hydroxyl groups and based on(meth)acrylic acid hydroxyalkyl esters having 2 to 12 carbon atoms inthe alkyl portion and optionally copolymerisable alpha,beta-unsaturatedmonomers, which are modified with cyclic esters of hydroxycarboxylicacid having 4 to 6 carbon atoms, with a number average molecular weightMn of 1000 to 10000, or

d) polyester polyols or polyether polyols, each having a number averagemolecular weight Mn of 500 to 2000.

Examples of group a) alkane di- and polyols are those having linear andbranched chains with 2 to 12 carbon atoms. They contain at least twohydroxyl functions, but preferably at least three.

Examples of these substances are propanediol, butanediol, hexanediol,glycerol, trimethylolpropane and pentaerythritol.

Examples of poly(meth)acrylates b) containing hydroxyl groups and basedon (meth)acrylic acid hydroxyalkyl esters having 2 to 12 carbon atoms inthe alkyl portion are hydroxyalkyl esters of acrylic acid or methacrylicacid with alcohols having at least two hydroxyl groups, such as 1,4-butanediol mono(meth)acrylate, 1,6 -hexanediol mono(meth) acrylate or1,2,3 -propanetriol mono(meth)acrylate. Examples ofpoly(meth)acrylamides b) containing hydroxyl groups and based on(meth)acrylic acid hydroxyalkylamides are amides of acrylic acid ormethacrylic acid with hydroxyalkylamines or di(hydroxyalkyl)amines eachhaving 2 to 12 carbon atoms in the alkyl portion, which may contain oneor more hydroxyl groups, such as acrylic acid hydroxyethylamide.

The component b) poly(meth)acrylates containing hydroxyl groups may behomo- or copolymers. They have a number average molecular weight (Mn) of1000 to 10000, preferably of 3000 to 6000 g/mol. Copolymerisablemonomers for the production of the copolymers are alpha,β-unsaturatedmonomers, free-radically polymerisable monomers from the groupcomprising esters of alpha,beta-unsaturated carboxylic acids, such asacrylic acid or methacrylic acid, wherein methyl, ethyl, propyl alcoholsand the isomers and higher homologues thereof are examples of thealcohol component. Further examples are diesters of maleic or fumaricacid, wherein the alcohol component is the same as mentioned above.Further examples are vinyl aromatic compounds, such as styrene,alpha-methylstyrene and vinyltoluene. Further examples are vinyl estersof short-chain carboxylic acids, such as vinyl acetate, vinyl propionateand vinyl butyrate.

The above-defined component c) poly(meth)acrylates containing hydroxylgroups may be modified poly(meth)acrylate homo- and copolymers, as aredescribed in b), the hydroxyl groups of which may be entirely orpartially reacted with cyclic esters, such as for example ofhydroxycarboxylic acids having 4 to 6 carbon atoms, such asgamma-butyrolactone or epsilon-caprolactone. The resultant modifiedcomponent c) poly(meth)acrylates have a number average molecular weightMn of 1000 to 10000.

Examples of component d) polyester polyols or polyether polyols arethose having a number average molecular weight Mn of 500 to 2000 g/mol.Specific examples are reaction products of di- or tricarboxylic acids,such as adipic acid or trimellitic acid, with polyols, wherein thepolyols are present in excess. Further examples are reaction products ofdi- or triols, such as propanediol, butanediol or glycerol, withethylene oxide or propylene oxide.

The binder composition according to the invention or the coatingcompositions according to the invention may optionally contain ascomponent D₁) one or more melamine resins as crosslinking agents.Examples of these are water-insoluble butanol- or isobutanol-etherifiedmelamines, such as for example the commercial products Setamin® US 138or Maprenal® MF 610; co-etherified melamines, which are etherified withboth butanol and methanol, such as for example Cymel® 254, together withhexamethyloxymethylmelamine (HMM melamines), such as for example Cymel®301 or Cymel® 303, wherein an acid catalyst, such as for examplep-toluenesulphonic acid, may be added to the latter for crosslinking.Further examples of melamine resin crosslinking agents are conventionalhydrophilic and thus water-soluble or water-compatible melamine resins,such as for example methyl etherified melamines, such as for exampleCymel® 325, Cymel® 327, Cymel® 350 and Cymel® 370, Maprenal® MF 927.

It is also possible to use the crosslinking agenttris(alkoxycarbonylamino)triazine. Examples of alkoxy groups are methoxyand butoxy groups.

The coating compositions according to the invention may contain ascrosslinking agents (component D₂) one or more free or cappedpolyisocyanates. Examples of polyisocyanates which may be used arecycloaliphatic, aliphatic or aromatic polyisocyanates, such astetramethylene diisocyanate, hexamethylene diisocyanate,2,2,4-trimethylene diisocyanate, 1,12-dodecane diisocyanate, 1,3- and1,4-cyclohexane diisocyanate,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethycyclohexane (=isophoronediisocyanate IPDI), perhydro-2,4'- and/or -4,4'-diphenylmethanediisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylenediisocyanate, 2,4'- and/or 4,4'-diphenylmethane diisocyanate, 3,2'-and/or 3,4-diisocyanato-4-methyldiphenylmethane, 1,5-naphthylenediisocyanate, 4,4',4"-triphenylmethane triisocyanate,tetramethylxylylene diisocyanate or mixtures of these compounds.

In addition to these simple isocyanates, those containing heteroatoms inthe isocyanate group linking residue are also suitable. Examples ofthese are polyisocyanates containing carbodiimide groups, allophanategroups, isocyanurate groups, urethane groups, acylated urea groups andbiuret groups.

Known polyisocyanates which are principally used in the production oflacquers are particularly suitable for the invention, for examplemodification products of the above-stated simple polyisocyanatescontaining biuret, isocyanurate or urethane groups, in particulartris-(6-isocynatohexyl)biuret or low molecular weight polyisocyanatescontaining urethane groups, as may be obtained by reacting excess IPDIwith simple monohydric alcohols of the molecular weight range from 62 to300, in particular with trimethylolpropane. Any desired mixtures of thestated polyisocyanates may, of course, be used for the production of theproducts according to the invention.

Suitable polyisocyanates are moreover known prepolymers having terminalisocyanate groups, as are in particular obtainable by reacting theabove-stated simple polyisocyanates, especially diisocyanates, withsubstoichiometric quantities of organic compounds having at least twogroups capable of reacting with isocyanate groups. The compounds usedare preferably those having a total of at least two amino groups and/orhydroxyl groups and a number average molecular weight of 300 to 10000,preferably of 400 to 6000.

In these known prepolymers, the ratio of isocyanate groups toNCO-reactive hydrogen atoms is 1.05 to 10:1, preferably 1.1 to 3:1,wherein the hydrogen atoms preferably originate from hydroxyl groups.

The nature and quantity ratios of the starting materials used in theproduction of NCO prepolymers are moreover preferably selected such thatthe NCO prepolymers have a) an average NCO functionality of 2 to 4,preferably of 2 to 3 and b) a number average molecular weight of 500 to10000, preferably of 800 to 4000.

The polyisocyanates may be used as free polyisocyanates. In this case,they are not capped. In this case, the systems are so-calledtwo-component systems (2-pack systems), in which the polyisocyanates areadded immediately before application. If the isocyanate groups of thepolyisocyanates are completely capped, the capped polyisocyanates maythen be added directly to the coating composition. In this case, thesystems are so-called one-component systems (1-pack systems).

Conventional capping agents, as are for example used in the lacquersector, may be used as the capping agent. Examples of usable cappingagents are malonic acid dimethyl ester, malonic acid diethyl ester,acetoacetic acid ethyl ester, epsilon-caprolactam, acetanilide,acetylacetone, acetone oxime, substituted pyrazoles, such asdimethylpyrazole, 1,2-propanediol and/or butanone oxime, wherein thelast stated capping agent is preferred.

The polyisocyanates may be capped, for example, by heating one or morepolyisocyanates with the capping agent. For example, one or morepolyisocyanates are initially introduced into a vessel and heated, forexample to 80° C., while being stirred and the capping agent isapportioned (for example over approximately 10 minutes). Stirring iscontinued until the NCO value is less than 0.1%. It is also possible tocap one or more polyisocyanates with a mixture of two or more cappingagents.

The advantage of using two or more different polyisocyanates and/or twoor more different capping agents is that crosslinking may consequentlybe performed over a wide range of temperatures.

If uncapped, free polyisocyanates are used in aqueous systems, it may beadvantageous to provide the polyisocyanates with hydrophilic orhydrophobic groups. The use of hydrophilic polyisocyanates facilitatestheir dispersion in water.

The introduction of hydrophobic groups accelerates the diffusion of thehydrophobised polyisocyanates into the resin particles in aqueoussystems. Hydrophilised polyisocyanates are familiar to the personskilled in the art, for example from EP-A-0 019 844, EP-A-0 061 628,EP-A0 310 345 and EP-A-0 540 985. Hydrophobised polyisocyanates aredescribed, for example, in the present applicant's unpublished Germanpatent application P 43 17 791.

The binder composition according to the invention and thus the coatingcompositions according to the invention may contain one or morecatalysts (component E). These are in particular catalysts soluble inorganic solvents or water or miscible with organic materials. Examplesof suitable catalysts soluble in organic solvents or miscible withorganic materials are phosphonium salts, such as for exampleethyltriphenylphosphonium acetate, phosphate, chloride, bromide, iodide,butyltriphenylphosphonium acetate, phosphate, chloride, bromide, iodide,benzyltriphenylphosphonium acetate, phosphate, chloride, bromide, iodideand quaternary ammonium salts, such as for examplealkylbenzyldimethylammonium chloride, benzyltrimethylammonium chloride,methyltrioctylammonium chloride, tetraethylammonium bromide,N-dodecylpyridinium chloride and tetraethylammonium iodide. Preferredcatalysts soluble in organic solvents or miscible with organic materialsare ethyltriphenylphosphonium acetate, phosphate, chloride, bromide,butyltriphenylphosphonium acetate, phosphate, chloride, bromide,benzyltriphenylphosphonium acetate, phosphate, chloride, bromide andmethyltrioctylammonium chloride. Ethyltriphenylphosphonium phosphatemay, for example, be obtained from ethyltriphenylphosphonium acetate byreaction with phosphoric acid. Another example of a catalyst isp-toluenesulphonic acid. It also possible to react theglycidyl-functionalised resin with p-toluenesulphonic acid, for exampleat elevated temperatures of up to, for example, 80° C. In so doing, thep-toluenesulphonic acid is attached with oxirane opening. When thecomplete lacquer is stored, the attachment is cleaved to yieldp-toluenesulphonic acid, which is capable of catalysing COOH-epoxidecrosslinking.

Further examples are dinonylnaphthalenedisulphonic acid,dinonylnaphthalenemonosulphonic acid and dodecylbenzenesulphonic acid.The acid catalysts may be partially, entirely or more than neutralised.Possible neutralising agents are tertiary amines, such as for exampletriethylamine, dimethylethanolamine or dimethyloxazolidine.

The catalyst soluble in organic solvents and/or water or miscible withorganic materials may be used in a quantity of approximately 0 toapproximately 10 wt. %, preferably of 0.3 to 2.0 wt. %, relative to thesum of weights of components A) to D₂).

It is also possible to link an amine catalyst to the COOH-functionalised(meth)acrylic copolymer resin mixture. This is conveniently achieved bycopolymerising tert.-amino(meth)acrylic monomers during synthesis of theCOOH-functionalised (meth)acrylic copolymer resin.

Examples of such monomers are dimethylaminoethyl (meth)acrylate,diethylaminopropyl (meth)acrylate and dimethylaminopropyl(meth)acrylate. The proportion by quantity of these (meth)acrylates isfrom 0.5 to 10 wt. %, preferably from 1 to 5 wt. %, relative to thetotal solids content of the COOH-functionalised (meth)acrylic copolymerresin.

When preparing the binder or coating composition according to theinvention, quantity ratios are preferably selected such that, betweenthe component A) resin containing carboxyl groups and the epoxycomponent B), there is a molar ratio of the reactive groups of 1:3 to3:1 and that, between the sum of the weights of components A) to C) andthe weight of the component D₁) melamine resin or of the cappedisocyanates D₂), there prevails a weight ratio of 65:35 wt. % to 98:2wt. % or of 60:40 to 95:5 wt. % respectively. The binder compositionsaccording to the invention may be used for the production of coatingcompositions. They may contain solvents, as are, for example,conventional for the production of coating compositions, for examplelacquers. The solvents may also be those as are used during productionof the individual components.

Examples of such solvents are organic solvents, such as aliphatic andaromatic hydrocarbons, for example toluene, xylene, mixtures ofaliphatic and/or aromatic hydrocarbons, esters, ethers and alcohols.These are conventional lacquer solvents. Aqueous solutions may also beprepared in order to produce coating compositions from the bindersaccording to the invention. Suitable emulsifiers, as are conventional inthe lacquer sector, may optionally be used for this purpose.

The binder compositions according to the invention, together with thecoating compositions according to the invention, may also be in aqueousform, wherein they contain no or only a small proportion of organicsolvents. In order to produce aqueous compositions, it is, for example,possible largely to eliminate organic solvents from component A)containing carboxyl groups, for example by distillation, and then toneutralise a proportion of the carboxyl groups, for example with basessuch as triethylamine or dimethylethanolamine and then to emulsify themin water, which is optionally heated. The other resins may thenoptionally be emulsified into this emulsifier resin. This is achieved,for example, by heating the emulsifier resin to 60°-80° C. and stirringin the hydroxy- and/or epoxy-functional resins, which have also beenheated to 60°-80° C., within 5 to 120 minutes.

It is also possible to mix the COOH-functionalised resin, from whichsolvents have largely been removed, with the epoxy resin, from which thesolvent has largely been removed, and to emulsify this in awater/emulsifier mixture using a rotor/stator unit. It is also possibleto emulsify the components separately and to mix the emulsions.

In order to produce the coating compositions according to the invention,pigments, extenders and/or conventional lacquer auxiliary substances andadditives may be added. These are conventional lacquer additives, as areusual in the lacquer sector.

Quantities are within the conventional ranges familiar to the personskilled in the art.

Examples of such additives are pigments, for example colouring pigmentssuch as titanium dioxide or carbon black and effect pigments such asmetal flake pigments and/or pearlescent pigments. The bindercompositions prepared according to the invention are also suitable forcoating compositions which contain such effect pigments. They preferablycontain effect pigments together with colouring pigments or colouringpigments together with extenders. Further examples of additives areconventional lacquer extenders, such as for example talcum andsilicates, together with auxiliary substances and additives such asplasticisers, light stabilisers, stabilisers and levelling agents, suchas silicone oil. These are also used in conventional quantities familiarto the person skilled in the art.

The coating compositions produced from the binders according to theinvention are suitable for coatings which adhere to many substrates,such as for example wood, textiles, plastics, glass, ceramics and inparticular metal.

The coating composition according to the invention may be applied usingknown methods, such as for example spraying, dipping, roller or knifeapplication. The topcoat lacquer coating is here applied onto thesubstrate, which has optionally already been provided with furtherlacquer layers. After a flashing off phase, the applied coatingcomposition is crosslinked by heating. Storing temperatures are from 20°to 180° C., preferably from 60° to 150° C. The thickness of the storedfilm is approximately 15 to 60 μm. The resultant crosslinked lacquercoating is hard, glossy and acid-resistant.

A preferred embodiment is the application of the coating compositionaccording to the invention as a clear lacquer coating on a base lacquer,preferably an aqueous base lacquer. The lacquer may be appliedwet-on-wet or the base lacquer is previously dried by heating. In thiscase, particularly good adhesion of the two layers is achieved.

Base lacquers which may contain conventional topcoat lacquer pigmentsmay, for example, be overpainted with the coating compositions accordingto the invention formulated without pigments as clear lacquers; the baselacquers preferably contain effect pigments, such as for examplemetallic pigments. The base lacquer binder is preferably based onpolyester, polyurethane or (meth)acrylic copolymer resins. These bindersmay optionally be crosslinked with crosslinking agents, for examplemelamine or isocyanate derivatives.

Some examples of further base lacquers which may preferably be coatedwith pigment-free clear or pigmented topcoat lacquers prepared accordingto the invention are listed below.

Aqueous base lacquers based on 5 to 95 wt. % of an aqueousepoxy-functionalised emulsion polymer and 95 to 5 wt. % of an anionicpolyurethane dispersion having an acid value of 5 to 10 mg of KOH/g.Suitable grinding resins for pigments and additives used in such aqueousbase lacquer are in particular (meth)acrylic copolymer resins (forexample in a quantity of up to 20 wt. %). Examples of such aqueous baselacquers are described in DE-A-36 28 124.

Base lacquers based on polyesters having a glass transition temperatureof >30° C., melamine resins (for example partially butylated melamineresins), polyurea plasticisers (for example based on an addition productprepared from butylurethane and formaldehyde) and a copolymer preparedfrom polyethylene (85 wt. %) / vinyl acetate (15 wt. %) as a waxdispersion. Such base lacquers may contain conventional additives, suchas cellulose acetobutyrate (for example having differing molecularweight ranges). Examples of such base lacquers are described in EP-A-187379.

One example of solvent-based base lacquers, which are particularlysuitable for repair purposes, contains physically drying binders basedon thermoplastic polyester and/or (meth)acrylic resin mixed withcellulose ethers or cellulose esters and/or polyvinyl acetates.Self-curing (meth)acrylic resin binders containing colour pigments andhaving hydrogen atoms which react with isocyanate are also present,together with mixtures of cellulose esters and/or cellulose semi-estersdissolved in solvents. Such lacquers are described, for example, inDE-OS 29 24 632.

All the above-stated base lacquer formulations may contain conventionallacquer additives, together with conventional extenders and colouringpigments as well as metal pigments such as aluminium or stainless steelbronzes and other effect pigments.

Examples of base lacquers which may be coated with clear lacquers basedon coating compositions according to the invention include powdercoatings, as are described, for example in Products Finishing, April1976, pages 54 to 56. It is also possible to heat the lacquer and applyit hot, for example at 60° to 100° C. In this manner, the lacquer may beapplied at an elevated application solids content as heating reducesviscosity.

It is also possible to combine the lacquer with supercritical carbondioxide as a lacquer solvent and to apply it using the so-called Unicarbprocess, as for example described in EP-A-0 321 607 and EP-A-0 388 927.

The coating compositions according to the invention may also beformulated as base lacquers and also as surfacers. They are thenparticularly well suited for the production of multi-layer lacquercoatings, for example in the automotive sector. Conventional additives,as were for example described above for base lacquers, may be added whenpreparing base lacquer or surfacer formulations.

In comparison with conventional base lacquers, the base lacquersaccording to the invention in particular give rise to coatings havingimproved resistance to warm, humid conditions.

The base lacquers according to the invention may be overpaintedwet-on-wet, optionally after short preliminary drying, with conventionalclear lacquers. They are preferably overpainted with clear lacquersbased on the coating compositions according to the invention.

In the following examples, unless otherwise stated, parts andpercentages relate to weight.

EXAMPLE 1)

Production of an epoxy-functional resin A

1250 parts of xylene are introduced into a 4 liter, three-necked flaskequipped with a stirrer, thermometer, dropping funnel and refluxcondenser and heated to reflux temperature (approx. 140° C.) while beingstirred.

A mixture of

750 parts of glycidyl methacrylate

155 parts of styrene

195 parts of butyl acrylate

100 parts of butyl methacrylate and

50 parts of tert.-butyl perbenzoate is added dropwise within 5 hours andthen post-polymerised for 6 hours.

The epoxy-functional resin has a solids content of 49.4% (1 hour, 150°C.).

For use in an aqueous clear lacquer (Example 7), the epoxy functionalresin is evaporated under a vacuum to a solids content of 82.7%.

EXAMPLE 2)

Production of a polyester oligomer B

336.7 g of trimethylolpropane, 366.8 g of adipic acid and 297 g ofhexanediol are melt-esterified with 5 g of hypophosphorous acid at 180°C. to 230° C. in a 2 liter, three-necked flask equipped with a stirrer,separator, thermometer and reflux condenser until an acid value of 20 isachieved.

The mixture is then condensed under a vacuum down to an acid value ofless than 1.5.

The resultant product has a storing residue of 94.5% (1 h, 150° C.), aviscosity of 3200 mPa.s (100%), a hydroxyl value of 460 and a colourindex of 30 Hazen.

EXAMPLE 3)

Production of a urethanised polyester oligomer C

850 parts of the polyester oligomer from Example 2) and 150 parts ofisophorone diisocyanate are weighed out into a 4 liter, three-neckedflask equipped with a stirrer, thermometer and reflux condenser andcarefully heated to 80° C.

Once the exothermic reaction is complete, the NCO value of the resin isreduced to less than 0.1 at 80° C.

Once this NCO value is achieved, 250 parts of xylene are added.

The resultant product has a storing residue of 77.5% (1 hour, 150° C.),a viscosity of 3100 mPa.s, a hydroxyl value of 320 mg of KOH/g and acolour index of 25 Hazen.

EXAMPLE 4

Introduction of carboxyl groups into the urethanised polyester oligomerC from Example 3

Once the product in Example 3) has been produced, 878 parts ofhexahydrophthalic anhydride are mixed in in a 4 liter, three-neckedflask equipped with a stirrer, thermometer and reflux condenser andesterified to a constant acid value at 80° C.

The carboxy-functional resin has a storing residue of 88.3% (1 hour,150° C.), a viscosity of 3800 mPa.s, an acid value of 320 mg of KOH/g(relative to solid resin) and a colour index of 25 Hazen.

EXAMPLE 5)

Chain extension with epsilon-caprolactone

In the apparatus from Example 4), 574 parts of epsilon-caprolactone areadded dropwise within 30 minutes to 1000 parts of the carboxy-functionalresin from Example 4. The reaction is performed at 140° C. until thetheoretical solids content is reached.

The chain-extended carboxy-functional resin containing urethane groupshas a solids content of 92.6% (1 hour, 150° C.), an acid value of 194 mgof KOH/g and a viscosity of 53000 mPa.s (25° C.).

EXAMPLE 6

Production of a clear lacquer composition

The following formulation is used for the preparation of a clear lacquercomposition

38.8 parts of chain-extended carboxy-functional resin containingurethane groups from Example 5)

58.9 parts of epoxy-functional resin from Example 1)

2.3 parts of diethylene glycol monobutyl ether

The solids content of the clear lacquer composition is 65.0%.

Using a knife, the clear lacquer from Example 6) is applied to a dryfilm thickness of approximately 40 μm onto a glass sheet and, after 10minutes' flashing off at room temperature, stored for 20 minutes at 140°C.

Pendulum hardness (Konig): 111 oscillations

H₂ SO₄ (10%, 65° C.): no marking after 20 minutes' exposure

Appearance: glossy

Xylene test: no marking or swelling after 10 minutes' exposure

EXAMPLE 7)

Production of an aqueous clear lacquer

a) Production of an aqueous emulsion

128 parts of a 10% solution of an emulsifier based on apolyoxypropylene-polyoxyethylene sorbitan diester and 0.1 parts of aconventional commercial defoamer are introduced into a 1 liter flask at60° C. The mixture is stirred with a stirrer rotating at a speed ofapproximately 8500 revolutions/minute. A mixture of 156 parts ofcarboxy-functional resin from Example 5) (solids content: 92.6%), 237parts of epoxy-functional resin from Example 1) (solids content: 82.7%)and 23 parts of completely deionised water are added within 3 minutes at60° C.

The resultant milky white emulsion has a solids content of 50.4%.

b) Aqueous clear lacquer composition

500 parts of emulsion from Example 7a

340 parts of completely deionised water

The aqueous clear lacquer has a solids content of 30%. It is appliedusing a spray gun (1.3 mm nozzle) to a dry film thickness ofapproximately 40 μm onto bright iron sheet or onto an iron sheet coatedwith a multilayer lacquer coating comprising an electrocoated primer,surfacer and aqueous base lacquer and, after 20 minutes' flashing off(10 minutes at room temperature, 10 minutes at 80° C.), stored for 20minutes at 140° C.

Properties of stored films:

on iron sheet:

pendulum hardness (Konig): 107 oscillations

in layer structure:

pendulum hardness: 85 oscillations

H₂ SO₄ (10%, 65° C.): no marking after 20 minutes' exposure

crosshatching test: rating 0-1 (very good to good)

xylene test: no marking or swelling after 10 minutes' exposure

We claim:
 1. Binder composition suitable for coating compositionscontainingA) 25 to 75 wt. % of the reaction product of one or morecarboxy-functionalised (meth)acrylic copolymers containing urethanegroups and/or of one or more carboxy-functionalised polyesterscontaining urethane groups, each having an acid value of 30 to 200 mg ofKOH/g, with one or more lactones, B) 25 to 75 wt. % of one or moreepoxy-functionalised crosslinking agents having at least two epoxyfunctions per molecule with a number average molecular weight (Mn) of200 to 10000 g/mol, C) 0 to 60 wt. % of one or more polyols having atleast two hydroxyl functions per molecule, D₁) 0 to 20 wt. % of one ormore melamine resins, D₂) 0 to 40 wt. % of one or more free or cappedpolyisocyanates, wherein the sum of the weight percentages of componentsA), B), C), D₁) and D₂) amounts to 100 wt. %, together with E) 0 to 10wt. % of one or more catalysts to catalyse the reaction of carboxyl andepoxy groups, relative to the sum of weights of components A) to D₂). 2.Binder composition according to claim 1, in which thecarboxy-functionalised (meth)acrylic copolymers containing urethanegroups have a number average molecular weight (Mn) of 500 to 10000 g/moland the carboxy-functionalised polyesters containing urethane groupshave a calculated molecular weight of 500 to 4000 g/mol.
 3. Bindercomposition according to claim 1, in which the resins of components A)and B) are at least partially precondensed.
 4. Binder compositionaccording to claim 1, characterised in that component B) was entirely orpartially produced in the presence of at least a proportion of componentC).
 5. Binder composition according to claim 4, characterised in thatcomponent C) is a hydroxy-functional polyester.
 6. Coating compositioncontaining the binder composition according to claim
 1. 7. Coatingcomposition according to claim 6 in the form of a lacquer containingsolvent.
 8. Coating composition according to claim 7 having a solventcontent of 2 to 60 wt. %.
 9. Coating composition according to claim 6which contains water and optionally one or more organic solvents. 10.Coating composition according to claim 6 in the form of a powdercoating.
 11. Coating composition according to claim 6 in the form of apigment-free and extender-free clear lacquer optionally containingconventional lacquer auxiliary substances and additives.
 12. Coatingcomposition according to claim 6 in the form of a topcoat or baselacquer containing pigments, extenders and/or conventional lacquerauxiliary substances and additives.
 13. Process for the production of acoating composition characterised in that, optionally after partialneutralisation of the carboxyl groups present, a binder compositionaccording to claim 1 is dissolved or dispersed in one or more organicsolvents and/or water and, before or after dissolution or dispersion, iscombined with conventional lacquer auxiliary substances and additives,pigments and/or extenders.
 14. Process for using coating compositionsaccording to claim 6 in pigmented forth for the production of single ormulti-layer lacquer coatings.
 15. Process for using coating compositionsaccording to claim 11 in pigment-free form for the production of clearlacquer layers.
 16. Process for using coating compositions according toclaim 6 in pigmented form for the production of base lacquer layers. 17.Process for using coating compositions according to claim 6 for theproduction of surfacer layers and/or base lacquer layers and/or clearlacquer layers in multi-layer lacquer coatings.
 18. Process for usingcoating compositions according to claim 6 for the production ofmulti-layer lacquer coatings in the automotive sector.